Vulcanized (per)fluoroelastomers are materials with excellent heat-resistance and chemical-resistance characteristics, which are generally used in the manufacture of sealing articles such as oil seals, gaskets, shaft seals and O-rings in which the leaktightness, the mechanical properties and the resistance to substances such as mineral oils, hydraulic fluids, solvents or chemical agents of diverse nature must be ensured over a wide range of working temperatures, from low to high temperatures, and wherein materials might be called to comply with severe requirements in terms of purity, plasma resistance and particles release.
One of the approaches for improving stiffness and mechanical properties is the use of fillers dispersed in the (per)fluoroelastomer matrix from which notably sealing articles can be obtained.
However, when the filler used is carbon black, in particular when it is used at high concentrations, a decline in the leaktightness and elongation at break properties (typical of elastic behaviour) is observed. Also use of carbon black is not possible for use in all those fields wherein high purity is required, e.g. for semi-con applications, for notably manufacturing sealing cured articles chemically compatible with the processes and equipments used during the fabrication of silicon wafers.
Within this latter field of use, the addition of polymeric fillers, in particular based on thermoplastic polymers based on tetrafluoroethylene (TFE), has made it possible to partially overcome such drawbacks: however, the sealing properties obtained with such fillers might still remain unsatisfactory, in particular when targeting sealing articles of high hardness. Further, in addition, the combination of the (per)fluoroelastomer and the filler still provides for a multiphasic mixture which might suffer from interfacial weaknesses, yielding e.g. delamination phenomena at the interfaces, and undergo particles release.
There is thus a continuous need for new additives suitable for being used in (per)fluoroelastomer compounds, which might provide improved mechanical properties (increased tensile module, increased hardness) combined with outstanding sealing properties (low values of compression set), with no risk of particles release nor contamination.